Galvanizing flux



Patented June 14;, 1949 UNITED STATES PATENT OFFICE GALVANIZING FLUXration of Delaware No Drawing. Application June 2, 1945, Serial No.597,382

4 Claims. 1

This invention relates to ammonium chloride fluxes for galvanizing andis more particularly directed to ammonium chloride fluxes which containsmall amounts of alkali metal chlorides, and which may additionallycontain small amounts of calcium chloride.

In the galvanizing of metal articles by dipping them in a bath of moltenmetal it is frequently the practice to provide a flux coating on top ofthe galvanizing bath to clean articles to be galvanized as they arelowered thru the flux layer into the molten metal. The best of thesefluxes are ammonium chloride, zinc ammonium chloride, orammoniumchloride mixed with zinc chloride, but even when newly appliedto a galvanizing pot these fluxes do not have sufficient activity incleaning articles to be galvanized and they do not have sufficientfluidity to meet the needs of modern galvanizing processes. Worse yet,these fluxes become inactive, viscous, and high melting after a periodof use. Consequently, it has been diificult consistently to producesmooth, uniform, and adherent metal coatings free from blemishes andthis difiiculty has increased When attempts were made to operategalvanizing processes at high speed.

The required characteristicsof a galvanizing flux may be tabulated:

1. A low melting point which permits the flux to become liquid when itcomes into contact with the molten metal bath with which it will beused. The freezing point should be as low as possible so that cold metalarticles may pass thru the flux without deleterious solidification whichwould result in the flux adhering to the article. The melting pointshould be low and should remain low during use of the flux.

2. Low viscosity so that the flux will flow readily around an articlepassed thru it so that it may quickly react and so that it will allowthe article to be withdrawn without dragging flux along with it. Theviscosity should remain low.

3. High chemical activity so that rust or other impurities which may bepresent on the surface of the article to be galvanized may quickly andeffectively be removed. The activity should continue at a high levelduring use of the flux.

It is particularly to be observed that for continuous strip galvanizingin which the article being galvanized passes rather rapidly thru theflux and thruthe galvanizing bath, an emphasis must be placed on highactivity, high fluidity, and low melting point.

It is an object oi this invention to provide flux compositions andprocesses which possessthe above tabulated characteristics and which areparticularly characterized by high activity, high fluidity, and lowmelting point so that they are particularly well adapted for continuousstrip galvanizing. It is a further object of this invention to provideflux compositions which have high activity to a steel surface and lowactivity to the galvanizing bath whereby less zinc is consumed by theflux to produce skimmings. It is a further object of this invention toprovide galvanizing fluxes which in use continue to have theabove-tabulated advantages. It is a further object of this invention toprovide galvanizing fluxes and galvanizing processes which in largemeasure overcome the disadvantages experienced by the prior art. It is astill further object to provide galvanizing fluxes and galvanizingprocesses which are simple and inexpensive. It is a still further objectto provide galvanizing fluxes and galvanizing processes by the use ofwhich galvanizing may be effected rapidly, uniformly, andsatisfactorily. Other objects will become apparent hereinafter.

The foregoing and other objects are attained by the inclusion in anammonium chloride fiux of a minor amount of a mixture of sodium andpotassium chloride which may additionally contain calcium chloride.

An ammonium chloride flux, according to the present invention, willordinarily contain from about to of ammonium chloride, from about '7 to15% of a mixture of sodium and p0- tassium chlorides, and from about 3to 5% of calcium chloride. The sodium and potassium chlorides willusually be used in about equal amount the generally there may be usedfrom about 70 to 30 parts by weight of potassium chloride.

While reference is made herein to the use of sodium chloride, potassiumchloride, and calcium chloride, it will be understood that equivalentsmay be used.

It will be understood, for instance, that there may be used either ametal chloride or a compound which under the conditions of use will beconverted to a chloride. Thus, there may be used such compounds as forma chloride by reacting with ammonium chloride in an aqueous pre-flux orby reacting under the conditions existing when brought into contact witha galvanizing bath in the presence of ammonium chloride. Numerouscompounds thus suitable will readily suggest themselves to those skilledin the art and as examples there may be suggested carbonates, acetates,hydroxides, or oxides of sodium, potassium, and calcium. Accordingly itwill be understood that when reference is made to the use of a chlorideof one of these metals an equivalent compound may be used instead of thechloride without departing from the spirit of this invention.

Flux compositions of the invention may contain various minor additionsin accordance with practices already set out in the art. They may, forinstance, contain foaming agents as set out in U. S. Patents 1,965,759,1, 965, 760, 2,106,982, and 2,123,949. It is to be observed that suchadditions are very minor in their amount, not ever. say, about 1 to 2%,and the flux compositions still are comprised essentially of ammoniumchloride and the sodium, potassium, and calcium chlorides as set outabove.

While it is preferred, as above indicated, to prepare compositionscomprising a mixture of ammonium chloride, sodium chloride, potassiumchloride, and calcium chloride, the components may be added separatelyto the molten flux on a molten metal bath, though it will be evidentthat such a procedure is not convenient. Alternativeif desired, theadded metal chlorides either with or without the other flux constituentsmay be dissolved in water thru which articles to be galvanized arepassed, and thus carried on the articles to the molten metal bath. Itwill also be apparent that compositions of the invention can be appliedas a top-flux to a galvanizing bath; they can be dissolved in water as apre-dip, or they can even be dusted on the surface of an article to begalvanized.

It will be understood that flux compositions according to the presentinvention whether added directly to the bath or added indirectly throughthe use of a flux wash should contain no deleterious materials.Fluorides, sulfates, and compounds of aluminum and of magnesium shouldin general be avoided. The presence of excessive a amounts of acids oracidulous salts should similarly be avoided and the compositions shouldnot be so constituted as to have an acidity equivalent to substantiallyless than about pH 3. In other words the flux compositions of thepresent inventions when dissolved in water should have an acidity ofabout pH 3 or more,

In order that the invention may be better understood reference should behad to the followin illustrative examples:

Example I A flux consisting of the following was made up and used aspre-flux:

Per cent Ammonium chloride 85 Sodium chloride 7.5 Potassium chloride 7.5

A solution consisting of 25 per cent by weight of the above mixture washeld at 160 F. while sheets of mild steel were dipped in them. When thesheets dried at room temperature, they tended to rust less than sheetsdipped in a 25 per cent solution of plain ammonium chloride. The sheetswere then galvanized by dipping them into molten zinc. Subsequentanalysis of the zinc indicated that the sheets dipped in the solutioncontaining ammonium chloride with sodium and potassium chlorides formedless dross than the sheets dipped in the ammonium chloride solution. Theflux of this example is particularly well adapted for use in continuousstrip galvanizing and it may be employed as a top flux in such use withexcellent results.

4 Example II A flux was made up as follows:

Per cent Sodium chloride 5 Potassium chloride 5 Calcium chloride 4Ammonium chloride 86 The flux thus prepared was found to have highactivity, high fluidity, and low melting point and was well suited foruse as a top-flux for continuous strip galvanizing. The addition ofabout one per cent of tallow, or about one-half of one per cent ofglycerol was .sufilcient to make the flux form a stable foam.

Example III A flux of the invention was made up as follows:

Per cent Ammonium chloride 89 Sodium chloride 35 Potassium chloride 3.5

Calcium chloride 4 The flux thus prepared was used on a zinc galvanizingpot and it was found to have a low melting point, a low viscosity, andhigh activity. The properties of the flux were excellent after ninehours of use while a flux made up similarly but omitting the sodium,potassium, and calcium 1. chlorides had become no longer usable byreason of an increase in viscosity and melting point.

The flux was particularly well adapted for use on continuous stripgalvanizing. It is also to be observed that when 1.10% of tallow wasused, in accordance with customary practices, the flux compositionfoamed in a most satisfactory manner.

While we have shown certain illustrative compositions and processes itwill be understood that one skilled in the art may readily devisenumerous similar compositions and processes without departing from thespirit of this invention. This application is a continuation-in-part ofour copending application Serial Number 437,032 filed March 31, 1942,now abandoned.

We claim:

1. A galvanizing flux for continuous strip galvanizing consistingessentially 7 to 15% of a mixture of sodium and potassium chlorides, andthe balance ammonium chloride, the mixture of sodium and potassiumchlorides containing '70 to 30 per cent by Weight of potassium chlorideand the balance being sodium chloride.

2. A galvanizing flux for continuous strip galvanizing consistingessentially 7 to 15% of a mixture of sodium and potassium chlorides, 3to 5% calcium chloride, and the balance ammonium chloride, the mixtureof sodium and potassium chlorides containing '70 to 30 per cent byweight of potassium chloride and the balance being sodium chloride.

3. In a galvanizing process the step comprising contacting an articleprior to galvanizing with a flux consisting essentially '7 to 15% of amixture of sodium and potassium chlorides, and the balance ammoniumchloride, the mixture of sodium and potassium chlorides containing '70to '30 per cent by weight of potassium chloride and the balance beingsodium chloride.

l. In a galvanizing process the step comprising contacting the articleprior to galvanizing with a flux consisting essentially 7 to 15% of amixture of sodium and potassium chlorides, 3 to 5% calcium chloride, andthe balance ammonium chloride, the mixture of sodium and potassium 5 6chlorides containing 70 to 30 per cent by weight UNITED STATES PA'I'ENTSof potassium chloride and the balance being Number I Name Date $dmmchlmde- 92,998 Peake July 27, 1869 ERNEST R. BOLLER. 1,941,750 JohanssonJan. 2, 1934 LOWELL D. EUBANK. 5 2,040,283 Swartz May 12, 1936 RAYMONDJ. KEPFER.

OTHER REFERENCES REFERENCES CITED International Critical Tables, Vol.IV, pages 45 The following references are of record in the m and 81,McGraw-Hill, New York (1928). file of this patent:

